Aqueous dispersion composition process for preparing the same, rust preventive, rust prevention method, and rust-proofed metallic products

ABSTRACT

An aqueous dispersion composition which comprises an ionomer resin (A) neutralized with a divalent metal, and water, sufficiently answers high level of requirement performances in various uses, and in particular, is particularly suitable as a heat sealing agent for aluminum foil, film, paper or the like, a metal coating agent, a modifier for various emulsions, a paint, an adhesive, a rust-preventive treating agent, and the like; a method which can produce the aqueous dispersion composition in high yield; a rust-preventive treating agent for a metal surface, which contains the aqueous dispersion composition, has excellent corrosion resistance, and can form a rust-preventive layer showing excellent coating adhesion to a over coat paint; a rust-preventive treatment method using the rust-preventive treating agent; and a rust-preventive treated metal product.

This application is the national phase under 35 U.S.C. §371 of prior PCTInternational Application No. PCT/JP98/02734 which has an Internationalfiling date of Jun. 19, 1998 which designated the United States ofAmerica.

FIELD OF THE INVENTION

The present invention relates to an aqueous dispersion composition and aprocess for producing the same, and rust-preventive agent, arust-preventive treatment method and a rust-preventive treated metalproduct.

BACKGROUND ART

It is well known that an ionomer resin comprising a macromolecular mainchain mainly constituted of a hydrocarbon, which is a partiallyneutralized product obtained by a part of carboxyl groups present on theside chain wish a metal cation has good adhesion to various substrates,in particular, metals. Further, it is known that since this ionomerresin can easily be dispersed in water, it is used as an aqueousdispersion. For this reason, an aqueous dispersion containing an ionomerresin has conventionally been used as a heat sealing agent for analuminum foil, a film or a paper, a metal coating agent, a modifier forvarious emulsions, a paint, an adhesive, a rust-preventive treatingagent, and the like.

However, in recent years, various properties are required for a coatingformed from an ionomer resin. When the conventional ionomer resin isused as an aqueous dispersion, there is the case that the coating cannotcope with such a diversity.

By the way, in recent years, based on the rise in environmentalproblems, there is a trend that a chromate treatment (treatment withhexavalent chromate or the like) which has conventionally been appliedto a rust-preventive steel plate is omitted. The coating itself formedby this chromate treatment has high degree of corrosion resistance andpainting adhesion, and reinforces the function of a rust-preventivelayer. Therefore, if this chromate treatment is not conducted, it ispresumed that the corrosion resistance and painting adhesion of therust-preventive steel plate markedly decrease. For this reason, therust-preventive treating agent used in rust-preventive treated metalplates has come to be required to form a rust-preventive layer havinghigher degree of corrosion resistance and painting adhesion than theconventional ones. A method of using an ionomer resin has conventionallybeen known as one of methods of forming a rust-preventive layer withoutconducting the chromate treatment.

However, the ionomer resin conventionally used for forming arust-preventive layer was a neutralized product of a monovalent metalsuch as Na or K, NH₃, or an amine, and the corrosion resistance wasinsufficient as a rust-preventive treating agent used for forming arust-preventive layer on a metal plate to which a chemical conversiontreatment such as a phosphate treatment or a chromate treatment is notapplied.

Further, an ionomer resin neutralized with a divalent metal such as Mgor Zn has conventionally been known. However, those ionomer resins havea low emulsifying property, and an aqueous dispersion cannot be obtaineda good yield. Thus, those have not been used as a treating agent in anaqueous dispersion.

Further, in recent years, with diversity and sophistication on use ofrust-preventive treated metal plates, for the purpose of colorationthere are increased cases that a coating comprising a curable resin suchas a paint is further formed on a rust-preventive treated metal platewhich has conventionally been used by merely treating a base material ofa substrate metal plate with a rust-preventive treating agent.

However, the ionomer resin has a poor adhesion to a coating comprising acurable resin such as a paint, and the rust-preventive layer comprisingthis ionomer resin does not show good painting adhesion to a coatingcomprising an over coat paint even if a paint or the like is coated overthe coating of the ionomer resin. Thus, a rust-preventive treated metalproduct having excellent adhesion between the rust-preventive layer andthe coating could not be obtained.

Furthermore, in recent years, high performances are required regardingcompatibility, adhesion and the like to a polar compound. However, theconventional ionomer resin having carboxyl group has not met such highrequirements.

DISCLOSURE OF THE INVENTION

Accordingly, a first object of the present invention is to provide anaqueous dispersion composition which sufficiently answers highrequirement performances, and in particular, is suitable as a heatsealing agent for aluminum foil, film, paper or the like, a metalcoating agent, a modifier for various emulsions, a paint, an adhesive, arust-preventive treating agent, and the like.

Further, a second object of the present invention is to provide a methodthat can produce the aqueous dispersion composition in high yield.

Further, a third object of the present invention is to provide arust-preventive treating agent for a metal surface, which contains theabove-mentioned aqueous dispersion composition, has excellent corrosionresistance, and can form a rust-preventive layer showing excellentadhesion to an over coat paint when the over coat paint is furthercoated on an upper layer.

Furthermore, a fourth object of the present invention is to provide arust-preventive treatment method which forms a rust-preventive layerhaving excellent corrosion resistance and showing excellent adhesion toan over coat paint when the over coat paint is coated on an upper layer,on the surface of a metal product using the above-mentionedrust-preventive treating agent.

Further, a fifth object of the present invention is to provide arust-preventive treated metal product having formed thereon arust-preventive layer having excellent corrosion resistance and showingexcellent adhesion to an over coat paint when the over coat paint iscoated on an upper layer.

To attain the first object, the present invention is to provide anaqueous dispersion composition comprising an ionomer resin (A)neutralized with a divalent metal, and water.

Further, to attain the second object, the present invention is toprovide a process for producing an aqueous dispersion compositionincluding the steps of mixing an ionomer resin (A) neutralized with adivalent metal, and a monovalent alkali metal compound, and emulsifyingthe same.

Further, to attain the third object, the present invention is to providea rust-preventive treating agent for a metal surface, comprising theabove-mentioned aqueous dispersion composition.

Furthermore, to attain the fourth object, the present invention is toprovide a rust-preventive treatment method which comprises coating theabove-mentioned aqueous dispersion composition on a metal surface toform a rust-preventive layer.

Further, to attain the fifth object, the present invention is to providea rust-preventive treated metal product obtained by the above-mentionedrust-preventive treatment method.

BEST MODE FOR CARRYING OUT THE INVENTION

An aqueous dispersion composition and a process for producing the same,and a rust-preventive treating agent, a rust-preventive treatment methodand a rust-preventive treated metal product of the present invention areexplained in detail below.

The aqueous dispersion composition of the present invention contains anaqueous dispersion comprising an ionomer resin (A), and water. Theionomer resin (A) forming this aqueous dispersion composition is apolymer comprising a polymeric main chain mainly consisting ofhydrocarbon, and having carboxyl groups at side chains, wherein at leasta part of the carboxyl groups is neutralized with divalent metalcations. A specific example of this ionomer resin can include an ionomerresin (A-1), which is an ethylene-unsaturated carboxylic acid copolymer,comprising a partially neutralized product obtained by neutralizing atleast a part of the carboxyl groups contained is neutralized with metalcations.

The ethylene-unsaturated carboxylic acid copolymer that constitutes amain skeleton of this ionomer resin (A-1) may be a random copolymer ofethylene and unsaturated carboxylic acid or a graft copolymer in whichunsaturated carboxylic acid is graft bonded to the main chain comprisingpolyethylene. In particular, the ethylene-unsaturated carboxylic acidrandom copolymer is preferable in the point that a coating havingexcellent transparency can be obtained. Further, thisethylene-unsaturated carboxylic acid copolymer may contain one kind ofunsaturated carboxylic acid only, or two kinds or more of unsaturatedcarboxylic acids.

The unsaturated carboxylic acid that is the component of theethylene-unsaturated carboxylic acid copolymer includes an unsaturatedcarboxylic acid having 3-8 carbon atoms or the like. Specific examplesof the unsaturated carboxylic acid having 3-8 carbon atoms includeacrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconicacid, crotonic acid, isocrotonic acid, citraconic acid, allylsuccinicacid, mesaconic acid, glutaconic acid, nadic acid, methylnadic acid,tetrahydrophthalic acid, and methylhexahydrophthalic acid. Of those,acrylic acid and methacrylic acid are preferable from the standpoint offilm-forming property.

Further, the ethylene-unsaturated carboxylic acid copolymer whichconstitutes the main skeleton of this ionomer resin (A-1) may contain athird component in addition to ethylene and the unsaturated carboxylicacid. This third component includes unsaturated carboxylic acid esterssuch as methyl (meth)acrylate, ethyl (meth)acrylate and isobutyl(meth)acrylate, and vinyl esters such as vinyl acetate.

The proportion of ethylene and the unsaturated carboxylic acid containedin the ethylene-unsaturated carboxylic acid copolymer is typically 95-60parts by weight of ehtylene and 5-40 parts by weight of the unsaturatedcarboxylic acid, and preferably 92-75 parts by weight of ethylene and8-25 parts by weight of the unsaturated carboxylic acid. Further, wherethe ethylene-unsaturated carboxylic acid copolymer contains a thirdcomponent, it is preferable for the third component to be contained inan amount of 40% by weight or less.

In this ionomer resin (A-1), at least a part of carboxyl groups that theethylene-unsaturated carboxylic acid copolymer has on the side chain isneutralized with divalent metal cations. The ionomer resin neutralizedwith monovalent metal cations is insufficient in corrosion resistance ofthe coating formed, and further the ionomer resin neutralized withtrivalent metal cations cannot yield the aqueous dispersion at goodyield. Further, the ionomer resin neutralized with NH₃, amine or thelike in place of the monovalent metal cation can easily form an aqueousdispersion, but corrosion resistance of the coating formed isinsufficient.

In the present invention, the divalent metal cation that the ionomerresin (A) has includes Mg, Zn, Ca, Cu, Fe and Ba. Of those, the ionomerresins having Mg and Zn as the divalent metal cations are preferable inthe point that the production is easy.

In the ionomer resin (A-1), the proportion of carboxyl groupsneutralized with divalent metal cations to all of carboxyl groups thatthe ethylene-unsaturated carboxylic acid copolymer has on the sidechain, that is, degree of neutralization, is generally about 20-100%,and preferably 30-80%, in the point that a coating having excellentcorrosion resistance is obtained. In particular, where the aqueousdispersion composition of the present invention is used as arust-preventive treating agent, this range is effective in the pointthat a rust-preventive layer having excellent corrosion resistance canbe formed.

Further, this ionomer resin has MFR (190° C.) by ASTM D 1238 ofpreferably 0.05-100 g/10 min, and particularly preferably 0.1-50 g/10min, from the standpoint of a film-forming property after baking anddrying.

The production of this ionomer resin (A-1) can be conducted according tovarious methods, for example, a method of copolymerizing ethylene,unsaturated carboxylic acid, and a third component used according to theneed, by a high pressure radical polymerization method, and neutralizingcarboxyl groups of the ethylene-unsaturated carboxylic acid copolymerobtained with a compound having the divalent metal cations; or a methodof graft polymerizing unsaturated carboxylic acid onto polyethylene, andneutralizing carboxyl groups of the graft copolymer obtained with acompound having the divalent metal cations. Further, this production maybe conducted by supplying predetermined components into an extruder andmelt kneading to conduct reaction, or may be conducted in water or anappropriate organic solvent.

The compound having the divalent metal cations includes ZnO, Zn(OH)₂,MgO, Mg(OH)₂, CuO, Ca(OH)₂, and Ba(OH)₂.

The aqueous dispersion composition of the present invention comprises anaqueous dispersion of the ionomer resin (A) as a main component, and maycontain at least one kind selected from an epoxy group-containingcompound (B) and a reaction product (C) of the ionomer resin (A)neutralized with the divalent metal cations and the epoxygroup-containing compound (B). That is, the aqueous dispersioncomposition of the present invention may be any composition comprisingthe combinations of each components in the following four aspects.

(1) Ionomer resin (A) alone

(2) Ionomer resin (A)+epoxy group-containing compound (B)

(3) Ionomer resin (A)+epoxy group-containing compound (B)+reactionproduct (C)

(4) Ionomer resin (A)+reaction product (C)

Of those, the compositions comprising the combinations of the above(2)-(4) are effective in that a coating having excellent adhesion to acoating comprising a curable resin or the like formed on an upper layercan be formed. This aqueous dispersion composition is appropriatelyselected according to formation or no formation of a coating on an upperlayer, a film-forming component used, film-forming conditions (treatmentconditions of, for example, baking the aqueous dispersion composition orthe film-forming component), and the like.

Where the aqueous dispersion composition of the present invention isused as the main component of a rust-preventive treating agent, thecomposition comprising the above-mentioned combinations of (2)-(4) areeffective in that a rust-preventive layer having excellent adhesion to acoating comprising a curable resin such as a over coat paint can beformed. In the rust-preventive treating agent, the combinations of(2)-(4) are appropriately selected according to necessity or unnecessityof a over coating, a paint used, film-forming conditions (bakingconditions of the rust-preventive treating agent or the over coatpaint), and the like.

The epoxy group-containing compound (B) used as a component of theaqueous dispersion composition of the present invention include glycidylesters obtained by the reaction of carboxylic acid and 2,3-epoxypropanolor the like; and alycidyl ethers obtained by the reaction ofepichlorohydrin and monovalent or polyvalent metal alkoxide.

The carboxylic acids for obtaining glycidyl esters include saturatedmonocarboxylic acids such as acetic acid, propionic acid, butyric acidor valeric acid; saturated dicarboxylic acids such as malonic acid,succinic acid, glutaric acid or adipic acid; aromatic carboxylic acidssuch as benzoic acid or phthalic acid; unsaturated monocarboxylic acidssuch as acrylic acid or methacrylic acid; and unsaturated dicarboxylicacids such as maleic acid, fumaric acid, itaconic acid, crotonic acid,isocrotonic acid, citraconic acid, allylsuccinic acid, mesaconic acid,glutaconic acid, nadic acid, methylnadic acid, tetrahydrophthalic acidor methylhexahydrophthalic acid. Those carboxylic acids may be containedin glycidyl esters in one kind alone or a combination of two kinds ormore.

Specific examples of the glycidyl esters used as the epoxygroup-containing compound (B) include adipic acid diglycidyl ester,phthalic acid diglycidyl ester, and terephthalic acid diglycidyl ester.

Further, the monovalent or polyvalent metal alkoxide for obtaining theglycidyl ethers used as the epoxy group-containing compound (B) is acompound obtained by the reaction of monohydric or polyhydric alcoholand a metal. Examples of the monohydric alcohol include methanol,ethanol, propanol, butanol, hexanol and phenol. Examples of thepolyhydric alcohol include ethylene glycol, resorcin, glycerin andbisphenol A. Examples of the metal include alkali metals or alkalineearth metals, such as lithium, sodium, potassium, magnesium and calcium.

Specific example of this monovalent or polyvalent metal alkoxideincludes sodium alkoxide. One kind alone or a combination of two kindsor more of those metal alkoxides may be contained in the glycidyl ether.

Specific examples of the glycidyl ethers used as the epoxygroup-containing compound (B) include sorbitol polyglycidyl ether,sorbitan polyglycidyl ether, polyglycidyl polyglycidyl ether,pentaerythritol polyglycidyl ether, diglycerol polyglycidyl ether,glycerol polyglycidyl ether, trimethylpropane polyglycidyl ether,neopentylglycol glycidyl ether, ethlene glycol diglycidyl ether,polyethylene glycol diglycidyl ether, propylene glycol diglycidyl ether,polypropylene glycol diglycidyl ether, and2,2-bis-(4′-glycidyloxyphenyl)propane.

The aqueous dispersion composition of the present invention may containthe above-mentioned glycidyl esters and glycidyl ethers in one kindalone or a combination of tow kinds or more.

In the present invention, of those epoxy group-containing compounds (B),polyvalent epoxy compounds of diglycidyl ether such as bisphenol Adiglycidyl ether, or ethylene and polyethylene glycol diglycidyl etherare preferable in the point that it can react with the ionomer resin (A)under heating to form a treating layer having excellent adhesion to acoating formed on an upper layer, and in particular, where the aqueousdispersion composition of the present invention is used as arust-preventive treating agent, a rust-preventive layer having excellentadhesion to a curable resin layer such as a over coat paint can beformed.

Further, the epoxy group-containing compound (B) may be a modified epoxyresin compound such as a reaction product of, for example, an aromaticepoxy resin compound represented by bisphenol A type epoxy resin with acarboxyl group-containing acrylic resin or an aromatic polyol resin.

Further, in the present invention, the epoxy group-containing compound(B) is preferably a water-soluble one or one which forms a dispersion,and in particular, is preferably a water-soluble one having a watersolubility of 25% or more, in the point that the preparation of theaqueous dispersion composition becomes easy. In the present invention,the water solubility means a proportion of the epoxy group-containingcompound actually dissolved in water when the epoxy group-containingcompound (B) is mixed with water at 25° C. That is, in the case that aninsoluble content of the epoxy group-containing compound (B) remains Y gwhen X g of the epoxy group-containing compound (B) is dissolved inwater at a certain temperature T, the water solubility of the epoxygroup-containing compound (B) at the temperature T is [(X−Y)/X]×100 (%).

Further, a viscosity of the epoxy group-containing compound (E) ispreferably 1-30,000 mPa·s, in particular, is preferably 5-20,000 mPa·s,at 25° C.

In the aqueous dispersion composition of the present invention, onehaving an epoxy equivalent in the range of generally 80-2,500, andparticularly 120-2,000, is used as the epoxy group-containing compound(B). In the present invention, the epoxy equivalent means a gram numberof he epoxy group-containing compound per gram equivalent of epoxygroup. For example, when an epoxy group-containing compound having amolecular weight of 100 has one epoxy group in one molecule, the epoxyequivalent of this epoxy group-containing compound is 100. Further, whenan epoxy group-containing compound having a molecular weight of 100 hastwo epoxy groups in one molecule, the epoxy equivalent of this epoxygroup-containing compound is 50.

The reaction product (C) of the ionomer resin (A) and the epoxygroup-containing compound (B), which is used as the component of theaqueous dispersion composition of the present invention, is formed byreacting carboxylic groups that the ionomer resin (A) has, with epoxygroups that the epoxy group-containing compound (B) has, in preparing acomposition containing the ionomer resin (A) and the epoxygroup-containing compound (B). This reaction product (C) is preferably awater-soluble one or one which forms a dispersion in the point that thepreparation of the aqueous dispersion composition is easy.

The aqueous dispersion composition of the present invention contains theionomer resin (A) in the form of an aqueous dispersion. Incidentally, ithas conventionally been known that an ionomer resin neutralized with amonovalent metal easily forms an aqueous dispersion, but it has beenknown that an ionomer resin neutralized with a divalent metal has lowemulsifying property, and can obtain an aqueous dispersion only in lowyield.

In the process for producing the aqueous dispersion composition of thepresent invention, it has been found that an aqueous dispersion of theionomer resin (A) neutralized with a divalent metal can be obtained ingood yield by also using a monovalent metal compound such as K or Na atthe time of the emulsification.

Examples of the monovelent metal compound used in the production processof the aqueous dispersion composition of the present invention includehydroxides such as KOH, NaOH or LiOH, and carbonates such as K₂CO₃ orNa₂CO₃. Of those, KOH and NaOH are particularly preferable.

In the production of the aqueous dispersion composition of the presentinvention, the monovalent alkali metal compound is generally preferablyused in an amount of 0.2-1 equivalent, particularly 0.5-0.95 equivalent,relative to the carboxyl group amount in an unneutralized state of theionomer resin (A).

In the production of the aqueous dispersion composition of the presentinvention, if a monovalent alkali metal compound is used, the ionomerresin (A) neutralized with a divalent metal can easily be emulsified. Ingeneral, the aqueous dispersion composition containing an aqueousdispersion of the ionomer resin (A) can easily be obtained by a methodof mixing the ionomer resin (A) having a solid content of 1-60 wt % towater and a monovalent alkali metal compound, heat melting at atemperature of 100-250° C., and dispersing.

In the aqueous dispersion composition of the present invention, theproportion of the ionomer resin (A) and water is desirably adjusted suchthat water is 100-2,000 parts by weight, and preferably 500-1,000 partsby weight, per 100 parts by weight of the ionomer resin (A), from thepoint of workability in coating formation. In particular, when theaqueous dispersion composition of the present invention is used as arust-preventive treating agent, it is desirable to adjust to this rangefrom workability of rust-preventive treatment.

Further, the viscosity of the aqueous dispersion composition of thepresent invention is preferably about 30-2,000 mPa·s, and particularlyabout 50-1,500 mPa·s, from workability of a coating formation in forminga coating using the aqueous dispersion composition of the presentinvention. In particular, when the aqueous dispersion composition of thepresent invention is used as a rust-preventive treating agent, it isdesirable to adjust to this range from the standpoint of workability ofcoating for forming a rust-preventive layer.

Further, a dispersion particle size of the aqueous dispersion of theionomer resin (A) in the aqueous dispersion composition of the presentinvention is generally 0.1 μm or less, and preferably 0.05 μm or less.

The aqueous dispersion composition of the present invention may becomposed of the above-mentioned ionomer resin (A) only, or may containthe aqueous dispersion of this ionomer resin (A), and the ionomer resin(A), the epoxy group-containing compound (B) and the reaction product(C) in any combination of the above-mentioned (2)-(4). In particular,when the aqueous dispersion composition of the present invention is usedas a rust-preventive treating agent, the aqueous dispersion compositioncontaining any combination of (2)-(4) can form a rust-preventive layerhaving excellent adhesion to a coating comprising a curable resin suchas a over coat paint, and therefore is useful.

The preparation of this aqueous dispersion composition can be conductedby, for example, a method of dissolving the epoxy group-containingcompound (B) in an aqueous dispersion of the ionomer resin (A), a methodof mixing an aqueous solution of the epoxy group-containing compound (B)with an aqueous dispersion of the ionomer resin (A), and a method ofheat melting a mixture of the ionomer resin (A), the epoxygroup-containing compound (B) and water and emulsifying in a batchmanner. In particular, the method of dissolving the epoxygroup-containing compound (B) in the aqueous dispersion of the ionomerresin (A), or that of mixing an aqueous solution of epoxygroup-containing compound (B) with the aqueous dispersion of the ionomerresin (A) is preferable. Those methods are preferably conducted at atemperature of normal temperature to 180° C.

Concentration of the ionomer resin (A), the epoxy group-containingcompound (B), and at least one kind selected from the reaction product(C) of the ionomer resin (A) and the epoxy group-containing compound(B), in the aqueous dispersion composition is not particularly belimited, and it can appropriately be adjusted according to the purposeof use, the method employed, the apparatus employed, and the like. Forexample, when the aqueous dispersion composition of the presentinvention is used as a rust-preventive treating agent, it isappropriately adjusted according to the coating method, the apparatusused for coating, and the like. The total amount of (A), (B) and (C) isgenerally 5-50% by weight, and preferably 10-40% by weight.

Further, in the aqueous dispersion composition of the present invention,the proportion of the ionomer resin (A), the epoxy group-containingcompound (B), and at least one kind selected from the reaction product(C) of the ionomer resin (A) and the epoxy group-containing compound (B)is preferably the ratio of (A)/[(B)+(C)]=99/1 to 50/50, and particularlypreferably (A)/[(B)+(C)]=90/10 to 60/40. When the aqueous dispersioncomposition of the present invention is used as a rust-preventivetreating agent, if the proportion of. the ionomer resin (A) exceeds theabove-mentioned range, the obtained adhesion of the rust-preventivelayer obtained to a over coat paint decreases, and on the other hand, ifthe proportion of the ionomer resin (A) is less than the above-mentionedrange, corrosion resistance of the obtained rust-preventive layerlowers.

The aqueous dispersion composition of the present invention may contain,according to the need, other components, for example, various resins,compounding agents, and the like in addition to the above-mentionedionomer resin (A), epoxy group-containing compound (B) and reactionproduct (C), within the range that the object of the present inventionis not impaired. Examples of the other components include water-solubleamino resins, curing agents, organic thickeners, inorganic thickeners,surface active agents, water-soluble polyvalent metal salts, and otherrust-preventive assistants, mildew proofing agents, ultravioletabsorbers, heat stabilizers, foaming agents, pigments, and fillers.

The water-soluble amino resin is used to improve strength of thecoating, and examples thereof include water-soluble melamine resin,hexamethoxymelamine, methylolated benzoguanamine resins and methylolatedurea resins. An example of the curing agent includes a phenolic resin.Further, the organic thickener or inorganic thickener is compounded inorder to improve stability of the composition and to adjust theviscosity. Examples of the organic thickener include polyvinyl alcohol,polyvinyl pyrrolidone, polyvinyl methyl ether, polyethylene oxide,polyacryl amine, polyacrylic acid, carboxymethyl cellulose, methylcellulose, and hydroxyethyl cellulose. Examples of the inorganicthickener include silicon dioxide, activated clay and bentonite.

The surface active agent is used to improve stability of thecomposition, and examples thereof include nonionic surface activeagents, and anionic surface active agents. Further, examples of thepigment include titanium white, red iron oxide, phthalocyanine, carbonblack and permanent yellow. Examples of the filler include calciumcarbonate, magnesium carbonate, barium carbonate, talc, aluminumhydroxide, calcium sulfate, kaolin, mica, asbestos, and calciumsilicate. Further, the rust-preventive assistant is used to improverust-preventive ability of a coating formed of the aqueous dispersioncomposition of the present invention, and includes water-solublepolyvalent metal salts such as molybdate.

The aqueous dispersion composition of the present invention isparticularly suitable as a rust-preventive treating agent for use in arust-preventive treatment method in which the composition is applied toa metal surface to form a rust-preventive layer having excellentcorrosion resistance and also good adhesion to a over coat paint.

When the aqueous dispersion composition of the present invention is usedas a rust-preventive treating agent, addition of inorganic oxide colloidsuch as silica or titanium oxide, other than the above-mentioned ionomerresin (A), and epoxy group-containing compound (B), or reaction product(C), is effective to improve corrosion resistance. The blending ratio isthe proportion of preferably 0-0.6, and more preferably 0.2-0.4, to[(A)+(B)+(C)]. If the blending ratio exceeds 0.6, adhesion between therust-preventive layer obtained and a metal surface decreases, andfurther in the case of coating a over coat paint on an upper layer ofthe rust-preventive layer, adhesion between the rust-preventive layerand a metal surface and also adhesion between a coating of the over coatpaint and the rust-preventive layer decrease, which is not preferable.

Examples of the metal plate to which the rust-preventive treatmentmethod is applied include various metal plates such as zinc-plated steelplate, zinc-based alloy-plated steel plate, aluminum-plated steel plate,aluminum-based alloy-plated steel plate, cold rolled steel plate and hotrolled steel plate. Further, the rust treatment method of the presentinvention is also applicable to zinc plates, aluminum plates and thelike. The metal plate applied may contain a slight amount of additionalelements.

In the rust-preventive treatment method of the present invention,coating the rust-preventive treating agent can he conducted by anymanner of spray, curtain, flow coater, roll coater, brush coating,dipping and the like. After coating the rust-preventive treating agenton a substrate, the agent may be spontaneously dried, but it ispreferable to conduct baking. The baking temperature is 60-250° C., andby heating for 1-120 seconds, a rust-preventive layer comprising acoating having good corrosion resistance can be formed.

In the rust-preventive treatment method, the thickness of therust-preventive layer formed on the substrate is appropriately selectedaccording to the purpose of use of rust-preventive treated metalproducts, rust-preventive treating agent used, kind, thickness or thelike of a over coat paint, and the like, and is not particularly limitedthereto. Generally, in order to exhibit sufficient rust-preventiveability without causing breakage in the rust-preventive layer whendrying after coating the rust-preventive treating agent, it ispreferable to coat in a thickness of 0.1-20 μm, and it is particularlypreferable to coat in a thickness of 0.3-10 μm.

In the rust-preventive treatment method of the present invention, theover coat paint coated on the rust-preventive layer formed with thetreatment by the rust-preventive treating agent preferably is a paintcomprising, for example, an acrylic resin, an acryl-modified alkydresin, an epoxy resin, an urethane resin, a melamine resin, a phthalicacid resin, an amino resin, a polyester resin or a vinyl chloride resin.Of those, a paint comprising an urethane resin, a melamine resin or anacrylic resin is preferable because of particularly excellent adhesionto the rust-preventive layer comprising the rust-preventive treatingagent of the present invention.

Further, this over coat paint may contain coloring pigments such astitanium white or carbon black, extenders such as talc, metal pigmentssuch as aluminum powder or copper powder, and rust-preventive pigmentssuch as red lead or lead sulfate, and the like. The paint may furthercontain dispersing agents, drying agents, plasticizers, defoamingagents, thickeners, stabilizers, anti-skinning agents, antimolds,antiseptic agents, antifreezing agents, and the like.

In the rust-preventive treated metal products produced by therust-preventive treatment method of the present invention, the thicknessof coating of the over coat paint is appropriately determined accordingto the purpose o0 use of the rust-preventive treated metal products,kind of the over coat paint used, and the like, and is not particularlylimited thereto. Generally, it is about 5-300 μm, and particularlypreferably 10-200 μm.

The formation of a coating of the over coat paint can be conducted bycoating the over coat paint on the rust-preventive layer, drying underheating, and curing. The drying time and temperature are appropriatelyadjusted according to the kind of the over coat paint coated, thethickness of the coating, and the like. Generally, it is 5-120 minutes,and particularly about 20-80 minutes. In a normal temperature curableover coat paint, curing is completed in about one week. The dryingtemperature is generally in the range of normal temperature to 200° C.,and in the range of particularly 50-150° C.

The rust-preventive treated metal products obtained by therust-preventive treatment method of the present invention have arust-preventive layer having excellent water resistance andrust-preventive property, and therefore can suitably be used as partsfor automobiles, household appliances, building materials, or the like.

EXAMPLE

Hereinbelow, the present invention will be explained concretly in moredetail by referring to the Examples and Comparative Examples, but theinvention concerned is not limited to those Examples.

Evaluation Method

(Preparation of Rust-preventive treated Metal Plate)

In Examples 1-3 and Comparative Example 1, a rust-preventive treatingagent comprising an aqueous dispersion composition was coated on azinc-plated steel plate, an iron-zinc alloy-plated steel plate, azinc-55% aluminum-plated steel plate or a cold rolled steel plate in adry coating thickness of 1 μm, and then baked under the conditions of200° C. (plate-reaching temperature: 130° C.) and 45 seconds to obtain arust-preventive treated metal plate sample.

Further, in Examples 4-5 and Comparative Examples 2-3, a melamine-alkydresin paint (AMIRAK, a product of Kansai Paint Co.) was further coatedon the rust-preventive treated metal plate sample obtained above byusing a bar coater in a dry coating thickness of 3 μm, and then bakedunder the conditions of 200° C. (plate-reaching temperature: 130° C.)and 45 seconds to obtain a sample for evaluation of adhesion of a overcoat paint.

(Emulsifying Property)

After producing an aqueous dispersion composition, it was filtered witha filter cloth of 100 mesh, and the amount of unemulsified product wasmeasured. The rest was considered as an emulsified product, and a yieldwas determined, which was used as a measure of the emulsifying property.

(Coating Adhesion)

According to the method of a cross-cut adhesion test described in JIS K5400, a test piece having formed thereon cross-cuts was prepared, and anadhesive tape (CELLOTAPE, trade name, a product of Nichiban Co.) wasadhered on the cross-cuts of the test piece. Thereafter, the adhesivetape was peeled by promptly pulling in the direction of 90°, and thenumber of cross-cuts which were not peeled in 100 cross-cuts wascounted. The value of (the number of cross-cuts not peeled)/100 was usedas the measure of adhesion, and evaluation was made in the followingcriteria.

Adhesion between rust-preventive layer and metal surface:

⊚: 100/100-90/100

◯: 80/100 or more and less than 90/100

Δ: 50/100 or more and less than 80/100

X: less than 50/100

Adhesion between rust-preventive layer and coating:

⊚: 100/100-90/100

◯: 80/100 or more and less than 90/100

Δ: 50/100 or more and less than 80/100

X: less than 50/100

(Corrosion Resistance of Non-coated Rust-preventive Layer)

According to the salt spray test method described in JIS Z2371, 5% NaClaqueous solution was sprayed to a non-coated rust-preventive treatedmetal plate sample at an atmosphere temperature of 35° C. Generationpercentage of white rust after 240 hours was measured, and corrosionresistance was evaluated by the following criteria.

X: Generation percentage of white rust is 100-50%.

Δ: Generation percentage of white rust is 25% or more and less than 50%.

◯: Generation percentage of white rust is 10% or more and less than 25%.

⊚: Generation percentage of white rust is less than 10%.

Example 1

240 g of an ethylene-methacrylic acid copolymer neutralized with Mg (MFR(1900° C.): 0.6 g/10 min, methacrylic acid content: 15 wt %, degree ofneutralization: 54%), 760 g of water and 18.8 g of potassium hydroxide(0.8 chemical equivalent to carboxyl groups of unneutralizedethylene-methacrylic acid copolymer) were introduced into a pressureautoclave having an inner volume of 1.5 liters. After raising thetemperature to 170° C., the resulting mixture was stirred for 2 hours toobtain an aqueous dispersion composition. The aqueous dispersioncomposition obtained had a solid content concentration of 25.0, aviscosity of 125, a pH of 11.5 and 100 mesh on (residual percentage ofsieve pass) of 0.02%. The yield of the aqueous dispersion was 97.2%.Using this aqueous dispersion composition as a rust-preventive treatingagent, it was conducted evaluation of corrosion resistance of anon-coated rust-preventive layer and evaluation of adhesion between arust-preventive layer and a metal surface. The results are shown inTable 1.

Example 2

250 g of an ethylene-methacrylic acid copolymer neutralized with Zn (MFR(190° C.): 0.7 g/10 min, methacrylic acid content: 15 wt %, degree ofneutralization: 58%), 750 g of water and 22 g of potassium hydroxide(0.9 chemical equivalent to carboxyl groups of unneutralizedethylene-methacrylic aid copolymer) were introduced into a pressureautoclave having an inner volume of 1.5 liters. After rising thetemperature to 170° C., the resulting mixture was stirred for 2 hours toobtain an aqueous dispersion composition. The aqueous dispersioncomposition obtained had a solid content concentration of 26.2, aviscosity of 123, a pH of 12.1 and 100 mesh on of 0.001%. The yield ofthe aqueous dispersion was 98.2%. Using this aqueous dispersioncomposition as a rust-preventive treating agent, it was conductedevaluation of corrosion resistance of a non-coated rust-preventive layerand evaluation of adhesion between a rust-preventive layer and a metalsurface. The results are shown in Table 1.

Example 3

240 g of an ethylene-methacrylic acid copolymer neutralized with Mg (MFR(190° C.): 0.6 g/10 min, methacrylic acid content: 15 wt %, degree ofneutralization: 54%), 760 g of water and 12.9 g of potassium hydroxide(0.55 chemical equivalent to carboxyl groups of unneutralizedethylene-methacrylic aid copolymer) were introduced into a pressureautoclave having an inner volume of 1.5 liters. After rising thetemperature to 170° C., the resulting mixture was stirred for 2 hours toobtain an aqueous dispersion composition. The aqueous dispersioncomposition obtained had a solid content concentration of 13.0, aviscosity of 10, a pH of 11.8, and 100 mesh on of 27%. The yield of theaqueous dispersion was 69%. Using this aqueous dispersion composition asa rust-preventive treating agent, it was conducted evaluation ofcorrosion resistance of a non-coated rust-preventive layer andevaluation of adhesion between a rust-preventive layer and a metalsurface. The results are shown in Table 1.

Comparative Example 1

275 g of an ethylene-methacrylic acid copolymer neutralized with Na (MFR(190° C.): 1.0 g/10 min, methacrylic acid content: 15 wt %, degree ofneutralization: 55%), and 725 g of water were introduced into a pressureautoclave having an inner volume of 1.5 liters. After rising thetemperature to 150° C., the resulting mixture was stirred for 2 hours toobtain an aqueous dispersion composition. The aqueous dispersioncomposition obtained had a solid content concentration of; 27.7, aviscosity of 515, a pH of 10.5 and 100 mesh on of 0.001%. The yield ofthe aqueous dispersion was 96.2%. Using this aqueous dispersioncomposition as a rust-preventive treating agent, it was conductedevaluation of corrosion resistance of a non-coated rust-preventive layerand evaluation of adhesion between a rust-preventive layer and a metalsurface. The results are shown in Table 1.

Example 4

50% aqueous solution of tetraethylene glycol diglycidyl ether wasprepared, and 2.5 g of this aqueous solution was added to 100 g of theaqueous dispersion composition obtained in Example 1, followed bystirring, thereby obtaining an aqueous dispersion composition. Usingthis aqueous dispersion composition as a rust-preventive treating agent,it was conducted evaluation of corrosion resistance of a non-coatedrust-preventive layer and evaluation of adhesion between arust-preventive layer and a coating and also between a rust-preventivelayer and a metal surface. The results are shown in Table 1.

Example 5

An aqueous dispersion composition was produced in the same manner as inExample 4 except that the aqueous dispersion composition obtained inExample 2 was used in place of the aqueous dispersion compositionobtained in Example 1. Using this aqueous dispersion composition as arust-preventive treating agent, it was conducted evaluation of corrosionresistance of a non-coated rust-preventive layer and evaluation ofadhesion between a rust-preventive layer and a coating and also betweena rust-preventive layer and a metal surface. The results are shown inTable 1.

Comparative Example 2

An aqueous dispersion composition was produced in the same manner as inExample 4 except that the aqueous dispersion composition obtained inComparative Example 1 was used. Using this aqueous dispersioncomposition as a rust-preventive treating agent, it was conductedevaluation of corrosion resistance of a non-coated rust-preventive layerand evaluation of adhesion between a rust-preventive layer and a coatingand also between a rust-preventive layer and a metal surface. Theresults are shown in Table 1.

TABLE 1 Corrosion Adhesion Adhesion Resistance between between inRust-preventive Rust-preventive Non-coated Layer and Layer and MetalPlate applied Test Coating Surface Metal Example 1 Zinc-plated steelplate ◯ X ⊚ Iron-zinc alloy-plated ◯ X ⊚ steel plate Zinc-55% aluminum-⊚ Δ ⊚ plated steel plate Cold rolled steel plate ◯ X ⊚ Example 2Zinc-plated steel plate ◯ — ⊚ Iron-zinc alloy-plated ◯ — ⊚ steel plateZinc-55% aluminum- ⊚ — ⊚ plated steel plate Cold rolled steel plate Δ —⊚ Example 3 Zinc-plated steel plate ◯ — ⊚ Iron-zinc alloy-plated ◯ — ⊚steel plate Zinc-55% aluminum- ⊚ — ⊚ plated steel plate Cold rolledsteel plate Δ — ⊚ Comparative Example 1 Zinc-plated steel plate X — ⊚Iron-zinc alloy-plated X — ⊚ steel plate Zinc-55% aluminum- X — ⊚ platedsteel plate Cold rolled steel plate X — ⊚ Example 4 Zinc-plated steelplate ◯ ⊚ ⊚ Iron-zinc alloy-plated ◯ ⊚ ⊚ steel plate Zinc-55% aluminum-◯ ⊚ ⊚ plated steel plate Cold rolled steel plate ◯ ⊚ ⊚ Example 5Zinc-plated steel plate ◯ ⊚ ⊚ Iron-zinc alloy-plated ◯ ⊚ ⊚ steel plateZinc-55% aluminum- ⊚ ⊚ ⊚ plated steel plate Cold rolled steel plate ◯ ⊚⊚ Comparative Example 2 Zinc-plated steel plate X ⊚ ⊚ Iron-zincalloy-plated X ⊚ ⊚ steel plate Zinc-55% aluminum- Δ ⊚ ⊚ plated steelplate Cold rolled steel plate X ⊚ ⊚

Comparing the results in Examples 1-3 and Comparative Example 1 shown inTable 1, it is understood that the rust-preventive treating agent of thepresent invention containing an aqueous dispersion of an ionomerneutralized with Zn or Mg forms a rust-preventive layer having excellentcorrosion resistance as compared with the rust-preventive treating agentof Comparative Example 1 containing an aqueous dispersion of an ionomerneutralized with Na.

Further, comparing the results in Examples 4 and 5 and comparativeExample 2 shown in Table 1, it is understood that by using an epoxygroup-containing compound together, the rust-preventive treating agentof the present invention containing an aqueous dispersion of an ionomerneutralized with Zn or Mg maintains its excellent corrosion resistance,and also adhesion between a rust-preventive layer and a coating of aover coat paint increases.

Example 6

A rust-preventive treating agent comprising an aqueous dispersioncomposition was prepared by further adding silica colloid (trade name:SNOWTEX N, a product of Nissan Chemical Industries, Ltd.) to the aqueousdispersion composition obtained in Example 1 in the solid content weightratio of silica colloid/aqueous dispersion shown in Table 2. Thisrust-preventive treating agent was coated on a zinc-plated steel plateto form a sample having a rust-preventive layer with a thickness of 1μm. Evaluation of corrosion resistance of a non-coated rust-preventivelayer and evaluation of adhesion between a rust-preventive layer and ametal surface were made on this sample. The results are shown in Table2.

TABLE 2 Ratio of Generation Adhesion between Silica Colloid/ Percentageafter Rust-preventive Aqueous Salt Spray Test Layer and Metal Dispersion(%) Surface Example 6 0 ◯ ⊚ 0.05 ◯ ⊚ 0.1 ◯ ⊚ 0.2 ⊚ ⊚ 0.4 ⊚ ⊚ 0.6 ⊚ ◯ 0.7⊚ Δ 1.0 ⊚ X

From the results of Example 6 shown in Table 2, it is understood thatcorrosion resistance is further improved by adding silica colloid.Further, it is understood that if the solid weight ratio of silicacolloid/aqueous dispersion exceeds 0.6, adhesion between arust-preventive layer and a metal surface decreases.

Industrial Applicability

The aqueous dispersion composition of the present invention sufficientlyanswers high degree of the required performances, and in particular, issuitable as a heat sealing agent for aluminum foil, film, paper or thelike, a metal coating agent, various emulsion modifiers, a paint, anadhesive, a rust-preventive treating agent, and the like.

Also, according to the production process of the aqueous dispersioncomposition of the present invention, the above-mentioned aqueousdispersion can be produced in high yield.

Further, the rust-preventive treating agent of the present invention canform a rust-preventive layer having excellent corrosion resistance andalso showing excellent adhesion to a over coat paint when the over coatpaint is coated on its upper layer. For this reason, the rust-preventivetreating agent of the present invention is suitable as a rust-preventivetreating agent for a zinc-plated steel plate, a zinc-based alloy-platedsteel plate, an aluminum-plated steel plate, an aluminum-basedalloy-plated steel plate, a cold rolled steel plate, a hot rolled steelplate, an aluminum plate, an aluminum alloy plate, and the like.

Furthermore, according to the rust-preventive treatment method of thepresent invention, a rust-preventive layer having excellent corrosionresistance and also excellent adhesion to a over coat paint can beformed on the surface of metal products.

Further, the rust-preventive treated metal product of the presentinvention has a rust-preventive layer comprising the above-mentionedrust-preventive treating agent on its surface, thus showing excellentcorrosion resistance, and also shows excellent painting adhesion to aover coat paint.

What is claimed is:
 1. An aqueous dispersion composition comprising: (A)an ionomer resin neutralized with at least one divalent metal selectedfrom the group consisting of Mg and Zn, (B) at least one epoxygroup-containing compound, (C) a reaction product of the (A) ionomerresin and the epoxy group-containing compound, wherein components (A),(B) and (C) are present in the proportion of (A)/((B)+(C))=99/10 to50/50, and (D) water.
 2. A process for producing an aqueous dispersioncomposition comprising a step of mixing: (A) an ionomer resinneutralized with at least one divalent metal selected from the groupconsisting of Mg and Zn, (B) at least one an epoxy group-containingcompound, (C) a reaction product of (A) the ionomer resin and (B) theepoxy group-containing compound, wherein components (A), (B) and (C) arepresent in the proportion of (A)/((B)+(C))=99/10 to 50/50, and (D) amonovalent alkali metal compound to emulsify said aqueous dispersion. 3.A rust-preventive treating agent for a metal surface, comprising anaqueous dispersion of: (A) an ionomer resin neutralized with at leastone divalent metal selected from the group consisting of Mg and Zn, (B)a least one epoxy group-containing compound, and (C) a reaction productof (A) the ionomer resin and (B) the epoxy group-containing compound,wherein components (A), (B) and (C) are present in the proportion of(A)/((B)+(C))=99/1 to 50/50, wherein said rust-preventative treatingagent for a metal surface prevents rust.
 4. A rust-preventive treatmentmethod, which comprises the steps of: coating a rust-preventive treatingagent onto a metal surface to form a rust-preventive layer, saidrust-preventive treating agent for a metal surface comprising an aqueousdispersion of: (A) an ionomer resin neutralized with at least onedivalent metal selected from the group consisting of Mg and Zn, (B) acleast one epoxy group-containing compound, and (C) a reaction product of(A) the ionomer resin and (B) the epoxy group-containing compound,wherein components (A), (B) and (C). are present in the proportion of(A)/((B)+(C))=99/1 to 50/50.
 5. A rust-preventive treatment method,which comprises the steps of: (i) coating a rust-preventive treatingagent onto a metal surface to form a rust-preventive layer, saidrust-preventive treating agent for a metal surface comprising an aqueousdispersion of: (A) an ionomer resin neutralized with at least onedivalent metal selected from the group consisting of Mg and Zn, (D) atleast one epoxy group-containing compound, and (E) a reaction product of(A) the ionomer resin and (B) the epoxy group-containing compound,wherein components (A), (B) and (C) are present in the proportion of(A)/((B)+(C))=99/1 to 50/50, and (ii) applying an overcoat paint on therust-preventative layer to form a coating.
 6. A rust-preventive treatedmetal product obtained by the steps of: coating a rust-preventivetreating agent onto a metal surface to form a rust-preventive layer,said rust-preventive treating agent for a metal surface comprising anaqueous dispersion of: (A) an ionomer resin neutralized with at leastone divalent metal selected from the group consisting of Mg and Zn, (F)at least one epoxy group-containing compound, and (G) a reaction productof (A) the ionomer resin and (B) the epoxy group-containing compound,wherein components (A), (B) and (C) are present in the proportion of(A)/((B)+(C))=99/1 to 50/50.
 7. The rust-preventive treated metalproduct as claimed in claim 6, wherein said metal product comprises azinc-plated steel plate, a zinc-based alloy-plated steel plate, analuminum-plated steel plate, a cold rolled steel plate, an aluminumplate, or an aluminum alloy plate.